I agree its pretty extreme, but as you said there will be some who definitely want it. Most of my testers committing right now are pretty damn serious... some extremely so and for them its right down their alley. I do believe it has likely potential to be harder on the trans, just because of the shock force on launch hitting the shafts etc.If there are unused pins, that would make it trivial. Going through the filter would work, but that's a bit sketchy. I wonder how many people would even want trans brake, that's fairly hard core drag racing for setups where brake boosting won't work. It's a bit of a parts killer, too. That said, I'm sure some will definitely want.
At some point I'm going to see if I can find any front diffs that bolt up to the N54 that are a bit beefier, it's been on my list for a while but I just haven't had time.
If you figure out something with the front diff please let me know, I will start on that later this year/early 2022. I would be happy to share what I find out as well.